Treatment of phosphatic material



Patented Nov. 22, 1932 UNITED STATES PATENT OFFICE BTAPLETON D. GOOCH, OF LAKE WALES, FLORIDA, .A SSIGNOB TO CORONET PHOSPHATE COMPANY, OF NEW YORK, N. Y, A CORPORATION OF NEW YORK TREATMENT OF PHOSPHATIC MATERIAL 80 Drawing.

This invention relates to the treatment of phosphatic material.

In the ordinary method of preparing raw hosphatic material for the manufacture of ertilizer, the material from the mine 1s screened or sized and then sent to a log washer to remove adherent sand, clay, and soft phosphate from the hard pebble. Thereafter the rock is subjected to a further washing or rinsing operation. After this treatment the rock is quite wet and in order to pre are it for subsequent treatment for the manu acture of fertilizer it must be dried.

The drying of the wet rock is usually done by heating it in a rotary kiln. In the OI'dlnary method crude oil is used as the fuel for the kiln. After this drying operation the material is then ready for shipment to the fertilizer plant.

An object of the present invention is to provide a novel method of drying wet phosphate rock.

Another object is to devise a method of treating phosphatic raw material to appreciably increase the P 0 A further object1 is to dlevise atrpethodtlqf d 'n wet hos ate roc y u i izing e m t er i als evc ehtua ily produced from the rock.

Yet another object is to devise a simple method of increasing the availability of phosphate rock.

An additional object is to effect economy in the preparation of phosphate fertilizer by subjecting wet phosphate rock to a prelim nary treatment to dry the materlal and s1- multaneously to partially convert it to an available form.

With these and other equally important objects in view the invention comprehends the concept of generating drying beats in situ in the wet rock and by means of a material which is a potentially available conversion re-agent for the rock.

To enable a ready comprehension of the invention a preferred method will be hereinafter described, but it will be understood that the treatment and material specified are merel illustrative and are to be considered as in icative of the equivalent steps and sub- 1930. Serial No. 433,185.

-of combustion of which is utilized to expel the water from the rock. The preferred pirogenetic substance is elemental phosp orus. This material may be fed, either as a sludge or as a substantially solid mass, into the kiln at a point ad'acent the entrant position of the rock, or t e streams of rock and phosphorus may be combined and the single or confluent stream then led directly to the burner or kiln.

It will be appreciated that the method and place of admission of the two materials, as well as the particular mechanisms utilized, may be widely varied. Thus the materials may be conveyed to the inlet end of the drier by a belt or screw conveyors or by any other suitable means. These are mechanical arrangements which may be varied as desired to adapt and accommodate the resent process to any particular existing equipment.

Simu taneousl with the admission of the rock and phosp orus there is injected into the kiln a stream of air of sufficient volume to insure complete oxidation of the phosphorus. This air may be admitted under natural or forced draft. In these circumstances, the phosphorus ignites and the heat of combustion generated, so to speak, in situ expels or drives off the moisture in the rock. Due to the presence of water vapor and to the large contact surface afforded by the rock a certain amount of phosphoric acid is formed. The phos horic acid so formed reacts with the trica cium phosphate to form citrate soluble phosphate. ThlS simple treatment, therefore, effects two desirable results; it dries the wet phosphate and simultaneously increases the P 0 content of the rock. This increase in P 0 content is additionally advantageous because of the fact that it is largely in an available form. This material, therefore, presents an excellent raw material for subsequent treatment with acid in the manufacture of phosphate fertilizers. Inasmuch as it contains a large percentage of available phosphate less acid is required in making up super or double super phosphates or any fertilizer mixtures.

The excess P 0 formed by the combustion of the phosphorus passes out of the drier, at the discharge end, and is then admitted to a suitable absorption system wherein it is sprayed with phosphoric acid or to a Cottrell precipitator wherein it is collected as strong phosphoric acid, or if desired, it may be passed through both of these systemsin series.

It will be observed that the present method at once provides a process for drying phosphate and/0r enriching phosphate. The water necessary for the humidification of the P 0 may be derived either from water contained in the rock or from water used as a vehicle for the elemental phosphorus. T herefore, the method is applicable to substantially dry phosphate rock for the purpose of increasing its P 0 content. In such a treatment the water necessary for the production of phosphoric acid is furnished by the aqueous vehicle of the elemental phosphorus. Furthermore, it is to observed that the drying of the phosphate rock is more effectively carried out due to the fact that the heat of oxidation of the phosphorus is generated, so

to speak, in situ, that is to say, directly in contact with and uniformly disseminated through the mass.

It is to be observed that the process is susceptible of many variations and ramifications. For example, if it is desired to increase the P 0 content to the optimum degree, the rock may be finely divided before admitting it to the dryer. It is to be observed here that since the process is applicable to wet rock the economies derived from wet grinding may be obtained. \Vith a fine subdivision of the rock a greater reactive surface is presented and a consequent increase in the quantity of the reaction products is secured. This reaction'may, of course, be increased by supplementing the action of the phosphoric acid formed in the dryer with that admitted to the dryer from the absorption tower or Cottrell precipitator.

While the process has been described as involving the utilization of elemental phosphorus it is to be understood that it is not necessarily limited to this material. The concept of drying wet phosphate rock by heats generated in the body of the rock may be efl'ectuated by using other oxidizable materials. Elemental phosphorus is preferred for a number of reasons. In the first place, it enables the system to be, so to speak, self-contained. In lieu of using fuel oil as a means of deriving drying heats, elemental phosphorus obtained by the pyrolysis under reducing conditions of a phosphate silica mixture may be employed. In this manner the product of one of the units (an electric or fuel invention is not limited to the use of a material such as phosphorus which subserves all of the improved functions described herein.

Other materials which will oxidize and whoseheat of oxidation may be utilized to dry wet phosphate rock may be employed. terials as will accomplish any or all of,the described functions and results are considered as being comprehended within the spirit of the invention.

I claim:

1. The method of drying moist hosphatic material comprising mixing phosp orus with the material and then burning the phosphorus in contact with the material, while maintaining the temperature below that at which phosphorus in the phosphate rock is reduced and volatilized.

2. The method of drying and enriching phosphate rock comprising burning f-ree phosphorus in contact with the rock and maintaining the temperature below that at which phosphorus in phosphate rock would be reduced and volatilized.

3. The method of drying phosphate rock comprising simultaneously feeding the rock and elemental phosphorus to a rotary burner and eflecting combustion of the phosphorus therein.

4. The method of drying and increasing the P 0 content of hosphate rock comprising simultaneously eeding moist phosphate rockand phosphorus into a combustion zone, causing combustion of the phosphorus therein in direct contact with the rock to thereby utilize the heat of combustion of the phosphorus to dry the rock and absorbing at least a part of the phosphoric acid produced in the rock and thereby effect a partial conversion of unavailable phosphatic material to an available form.

5. The method of drying and enriching moist phosphatic material comprising adding elemental phosphorus to the moist material generating P 0 in situ in the material to thereby utilize the heat of combustion of the phosphorus to dry the material, forming phosphoric acid therefrom in contact with and from moisture derived from the materia 6. The method of enriching and drying wet phosphate rockcomprising simultaneously feeding rock and elemental phosphorus to a rotary burner agitating the mixture in said burner causing combustion of the phos- Such maphorus therein, absorbing some of the P 0. by the rock, and utilizing the heat of combustion of the phosphorus to expel moisture from the rock.

7. The method of treating wet phosphate 1 rock comprising simultaneously passing elemental phosphorus and the rock to a rotary burner, causing combination of the phosphorus, agitating and contacting the rock with the products of combustion to increase the P 0 content and discharging and' collecting the excess P 0 8. A method of drying moist phosphatic material comprising subjectin the materialto exothermic heat generated in situ by the formation of phosphorus pentoxide from the oxidation of free added phosphorus, and maintaining the temperatures sufliciently low to prevent the reduction and volatilization of phosphorus in the phosphatic material, but sufliciently high to expel excess water and to convert at least a portion of the phosphatic material to citrate soluble phosphate.

9. A method of enriching and drying moist phosphate rock comprising generating phosphorus pentoxide directly in contact with the phosphate rock by the combustion of added elemental phosphorus and humidifying the phosphorus pentoxide generated with water derived from the moist rock, thereby utilizing the heat of combustion of the phosphorus to expel water from the rock and to cause a conversion of, a portion of the rock to citrate soluble phosphate.

In testimony whereof I afiix my signature.

STAPLETON D. GOOCH. 

